There is a demand for high quality grass sod having substantially all of its soil removed. For instance, the U.S.G.A. requires that their putting greens have a specific sand and peat soil mixture beneath the grass of their greens. Growers try to grow their grass in a soil having the specified sand and peat mix, but frequently the soil content is incorrect or other materials such as clay inadvertently get into the sand and peat mix. Thus, groundkeepers at golf courses are required to take a garden hose to the grass sod and wash the soil from the sod prior to applying the grass sod to the putting green, in order to assure that the soil beneath the grass met the exacting specifications of the U.S.G.A. Since manually washing each length of grass sod prior to applying it to a putting green is time consuming and the golf course is not particularly well suited for carrying out such sod washing, there is a demand for grass sod which has already had substantially all of its soil removed prior to shipment, so that further washing at the golf course, or other recipient site, is not necessary.
Sod grass having the soil still remaining thereon does not bond to the soil to which it is applied as well as sod grass which already has substantially all of its soil removed prior to being laid. The reason for this is that the roots stay in the thin nutrient-rich layer of soil of the sod, and do not penetrate down into the subsoil onto which the sod is laid. In dry weather, the thin layer of soil dries out and the lack of roots extending down into the subsoil results in burning of the grass blades of the laid sod. To prevent burning, the laid sod must have a great deal of extra water supplied thereto. While the presence of extra water keeps the thin layer of soil of the sod moist, it causes the growth of detrimental fungus in the layer of intermeshed soil and roots. Since the roots of grass sod which has had its soil removed therefrom prior to being laid grow down into the subsoil, rather than remaining substantially within the thin layer of soil of the sod as experienced with sod which has not been cleaned prior to being laid, the cleaned grass sod can utilize moisture of the subsoil, and is not dependent on the moisture of the thin layer of soil. Thus, less watering is required and there is less likelihood of growth of fungus.
One method and apparatus for washing sod is disclosed in U.S. Pat. No. 4,063,384. However, the method and apparatus disclosed therein suffer numerous shortcomings. The patented method and apparatus imparts high pressure water jets onto the grass sod to use water at high pressure to wash the soil from the grass sod. One major shortcoming of this method is that the high pressure of the water blows holes through the sod in areas where the sod is not sufficiently thick, such as where a weed had been pulled or some other flaw.
Another shortcoming of the patented apparatus and method is that the high pressure water jets utilized therein stretch out the grass sod and shred or tear the edges of the sod sections. Such shredded or torn edges have been found to experience burnout significantly more frequently than sod sections in which the integrity of the edges is maintained. Also, the roughened edges make it difficult to accurately position the sod sections closely adjacent one another as desired. Holes or rough edges between pieces of sod are on undesirable golf course greens.
A golf green will typically use 1,600 rolls of sod that are 18 inches in width and six feet in length. In the Summer, it is best to be able to cut the sod, wash the sod, transport the sod, and lay it in the same day to prevent the roots from drying out. With the apparatus of U. S. Pat. No. 4,063,384, the production rate is about 300 to 325 rolls per hour which requires about four or five hours for washing alone, thereby making it more difficult to cut, wash, transport and lay the sod for a green in the same day.
Another shortcoming in the use of the apparatus of U.S. Pat. No. 4,063,384 is that of handling the water after washing the sod and the disposal of the soil removed from sod. Typically, the water is collected at the apparatus and piped back to a cooling pond and a water reclamation device may be used. After several hours of use of the apparatus, the water, which is pumped from the pond and piped for washing, may be somewhat dirty thereby leaving the grass more dirty than is than desirable. A typical roll of sod may weigh 22 pounds with about ten pounds of grass and grass roots left after washing, and with about 12 pounds of soil, thatch, etc. washed from the roll of sod. Sixteen hundred (1,600) washed rolls of sod need for one golf green results in a large amount of soil that must be transported away from the apparatus disclosed in U.S. Pat. No. 4,063,384. Also, when using reclaimed water in the aforesaid apparatus, the water temperature may drop to an extent on hot days such that the grass is not as cool as desired after washing.